Many of the experiences of everyday life induce emotional reactions, ranging from low to highly arousing. There has been substantial progress in understanding how adults process emotional events. The work has made clear that the ways in which individuals represent and express their emotional experiences has implications for mental health. Because of the importance of emotional construal to the quality of everyday life and to mental health, it is crucial that we understand emotion processing across the lifespan. Research with adults has revealed characteristic patterns of response to emotional stimuli as well as both individual and gender differences in processing of emotional experience. There also has been substantial research on expression and regulation of emotion early in development, as young children are beginning to learn about the causes and consequences of emotional experiences. In contrast, there has been little research on emotion processing in the elementary school years and into adolescence. As a result, we know little about the timing or course of developmental changes leading up to mature emotion processing. The proposed research will begin to fill these gaps by using the neuroimaging tool of event-related potentials (ERPs) to examine emotion processing in school-age children through middle adolescence. ERPs are ideally suited to examination of emotion processing due to their exquisite temporal resolution (on the scale of milliseconds), permitting observation of emotional responses in real time, as they are experienced. The work will be used to address two specific aims: (1a) examination of developmental changes in emotion processing in school- age children to young adolescents, with samples sufficiently large to permit examination of the emergence of gender-differential patterns of emotion processing that may be associated with internalizing and externalizing disorders (in females and males, respectively); (1b) examination of the emergence of patterns of neural response to emotional stimuli that are typical in adults, yet which to date have not been observed in children; and (2) examining emotion processing both as children process emotional stimuli for the first time and as they re-experience the events through memory, thereby providing a more complete perspective on developmental changes in emotion processing. The proposed research will elucidate the typical course of development of emotion processing in childhood through middle adolescence, when mature patterns of emotion processing are expected to become apparent. The research will be foundational for later translational work aimed at understanding emotion processing gone awry, such as observed in internalizing and externalizing disorders of childhood and adolescence. The combination of paradigms for examining processing of emotion in the moment and based on memory will be especially powerful, with high ecological validity.